Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H, W = map(int, input().split())
S = [[c for c in input()] for _ in range(H)]
a = sum([S[y][x] == "." for x in range(W) for y in range(H)])
dx = [1, -1, 0, 0]
dy = [0, 0, 1, -1]
B = [[-1]*W for _ in range(H)]
q = deque([(0, 0, 1)])  # y,x,step
while len(q) > 0:
    y, x, step = q.popleft()
    if y < 0 or H <= y or x < 0 or W <= x:
        continue
    if S[y][x] == '#' or B[y][x] >= 0:
        continue

    B[y][x] = step

    for i in range(4):
        q.append((y+dy[i], x+dx[i], step+1))
# print(*B, sep='\n')
print(a - B[H-1][W-1] if B[H-1][W-1] >= 0 else -1)